Indications for PT/PTT/INR

[aria_alice]

Hello, all. I know this is repetitive topic on the site but I'm still confused despite reading the other articles.

PT = measures time (secs) of blood to clot. Used to determine if pt has a bleeding disorder, or if coumadin therapy is adequate.

PTT = Same with PT but if heparin therapy is adequate.

INR = standardized ratio to determine efficacy of coumadin.

My question is, is PT only for coumadin, and is PTT only for heparin? I feel like I've seen patients who weren't on those meds and sometimes PT/PTT/INR were ordered. Was it just part of admission labs or am I missing something? Do we use PT/PTT/INR for other anticoags efficiency? Or is PT/PTT/INR used to determine blood clotting in general even if patient is taking no anticoags?

[PaSSiNGaS, MSN]

I'd recommend looking over the clotting cascades and you should find your answers. Heparin and Coumadin work on different parts. Sometimes patients aren't on either med but it's nice to know prior to surgery for bleeding risk or any deficiencies or may have.

[Steph41]

PT even if elevated is not the gold standard for Coumadin. INR is.

PTT - used not just for hep but also lovenox.

Beyond measuring effectiveness of meds, here is a few things to consider...

1. A huge percent of herbs and some foods effect the clotting cascade.

IF you were a surgeon would you cut on someone without knowing their coags and PLT counts?

also liver disease makes you coagulopathic. It will increase your PT,PTT,,INR with no help from meds. So the short answer is yes - they should be drawn on admission on any inpatient and as frequently indicated for pt.'s condition.

Hope that helps.

[Corey Narry, MSN, RN, NP]

Actually, low molecular weight heparins such as Lovenox does not typically affect PTT and INR and both are not used to assess the efficacy of therapy. These drugs have more stable absorption than heparin and don't necessarily require lab monitoring except for cases of those with extreme weights (the drug is dosed based on weight) or those with renal disease (usually contraindicated). You would measure anti-factor Xa level and specify to the lab that you are checking for Lovenox if you want to make sure that the Lovenox is working adequately.

Some places also use anti-factor Xa level for measuring heparin efficacy (with level specifically targeted for heparin).

Aside from monitoring Coumadin therapy, the INR is also used in liver disease as a measure of degree of coagulopathy/synthetic liver function and in determining MELD score (severity of liver failure). It is elevated in patients with malnutrition (such as those who are Vitamin K deficient).

Argatroban therapy, an anticoagulant that is not heparin-related, hence used in heparin induced thrombocytopenia, is monitored by checking PTT, it artifcially elevates INR (not used as a monitoring test due to this fact).

The NOAC's or Novel Oral Anticoagulants (i.e., rivaroxaban, apixaban) do not affect PTT, PT, INR and have no established monitoring tests.